The present invention generally relates to printing technology, and more particularly involves an improved, high-durability printhead structure for use in an ink cartridge (e.g. a thermal inkjet system). The present invention is related to U.S. patent application Ser. No. 08/921,675 "Improved Printhead Structure and Method for Producing the Same", filed on behalf of Lee Van Nice et al. on the same date hereof and assigned to the same assignee.
Substantial developments have been made in the field of electronic printing technology. Specifically, a wide variety of highly efficient printing systems currently exist which are capable of dispensing ink in a rapid and accurate manner. Thermal inkjet systems are especially important in this regard. Printing systems using thermal inkjet technology basically involve a cartridge, which includes at least one ink reservoir chamber in fluid communication with a substrate having a plurality of resistors thereon. Selective activation of the resistors causes thermal excitation of the ink and expulsion of the ink from the cartridge. Representative thermal inkjet systems are discussed in U.S. Pat. No. 4,500,895 to Buck et al.; U.S. Pat. No. 4,771,295 to Baker et al.; U.S. Pat. No. 5,278,584 to Keefe et al.; and the Hewlett-Packard Journal, Vol. 39, No. 4 (August 1988).
In order to effectively deliver ink materials to a selected substrate, thermal inkjet printheads typically include an outer plate member known as an "orifice plate" or "nozzle plate" which includes a plurality of ink ejection orifices (e.g. openings) therethrough. Initially, these orifice plates were manufactured from one or more metallic compositions including but not limited to gold-plated nickel and similar materials. However, recent developments in thermal inkjet printhead design have resulted in the production of orifice plates which are non-metallic in character, with the term "non-metallic" being defined to involve one or more material layers which are devoid of elemental metals, metal amalgams, or metal alloys. These non-metallic orifice plates are generally produced from a variety of different organic polymers including but not limited to film products consisting of polytetrafluoroethylene (e.g. Teflon.RTM.), polyimide, polymethylmethacrylate, polycarbonate, polyester, polyamide polyethylene-terephthalate, and mixtures thereof. A representative polymeric (e.g. polyimide-based) composition which is suitable for this purpose is a commercial product sold under the trademark "KAPTON" by E.I. DuPont de Nemours and Company of Wilmington, Del. (USA). Orifice plate structures produced from the non-metallic compositions described above are typically uniform in thickness, with an average thickness range of about 25-50 .mu.m. Likewise, they provide numerous benefits ranging from reduced production costs to a substantial simplification of the printhead structure which translates into improved reliability, performance, economy, and ease of manufacture. The fabrication of film-type, non-metallic orifice plates and the corresponding production of the entire printhead structure is typically accomplished using conventional tape automated bonding ("TAB") technology as generally discussed in U.S. Pat. No. 4,944,850 to Dion. Likewise, further detailed information regarding polymeric, non-metallic orifice plates of the type described above are discussed in the following U.S. Pat. No. 5,278,584 to Keefe et al. and U.S. Pat. No. 5,305,015 to Schantz et al.
However, a primary consideration in the selection of any material to be used in the production of an inkjet orifice plate (especially the polymeric compositions listed above) is the overall durability of the completed plate structure. The term "durability" as used herein shall encompass a wide variety of characteristics including but not limited to abrasion and deformation resistance. Both abrasion and deformation of the orifice plate can occur during contact between the orifice plate and a variety of structures encountered during the printing process including wiper-type structures (normally made of rubber and the like) which are typically incorporated within conventional printing systems.
Deformation and abrasion of the orifice plate not only decreases the overall life of the printhead and cartridge associated therewith, but can also cause a deterioration in print quality over time. Specifically, deformation of the orifice plate can result in the production of printed images, which are distorted and indistinct with a corresponding loss of resolution. The term "durability" also encompasses a situation in which the orifice plate is sufficiently rigid to avoid problems associated with "dimpling". Dimpling traditionally involves a situation in which orifice plates made of non-metallic, polymer-containing materials undergo deformation and become essentially non-planar. This condition is typically caused by physical abrasion of the orifice plate, and is likewise associated with the non-planar assembly of the printhead or the non-planar mounting of the printhead to the cartridge unit. Dimpling presents substantial problems including misdirection of the ink droplets being expelled from the printhead which results in improperly printed images. Accordingly, all of these factors are important in producing a completed thermal inkjet system, which has a long life-span and is capable of producing clear and distinct images throughout the life-span of the system.
Prior to development of the present invention, a need existed for an inkjet orifice plate manufactured from non-metallic organic polymer compositions (as well as metallic compounds) having improved durability characteristics. Likewise, a need remained for a printhead having a high level of structural integrity. The present invention satisfies these goals in a unique manner by providing a specialized printhead structure which is characterized by improved durability levels, with these components being applicable to both thermal inkjet and other types of inkjet printing systems. Accordingly, the claimed invention represents a substantial advance in inkjet printing technology as discussed in detail below.